His most famous work on alchemy is the Amphitheatrum Sapientiae Aeternae (Amphitheater of Eternal Wisdom), a work on the mystical aspects of that art, which contains the oft-seen engraving entitled "The First Stage of the Great Work", better-known as the "Alchemist's Laboratory". The book was first published at Hamburg in 1595, with four circular elaborate, hand-colored, engraved plates heightened with gold and silver which Khunrath designed and were engraved by Paullus van der Doort. The book was then made more widely available in an expanded edition with the addition of other plates published posthumously in Hanau in 1609. Amphitheatrum Sapientiae Aeternae is an alchemical classic, combining both Christianity and magic. In it, Khunrath showed himself to be an adept of spiritual alchemy and illustrated the many-staged and intricate path to spiritual perfection.